He created this non-factory (wildcat) offering by simply necking-down the .22 Hornet to .17 caliber and fire-forming the resized cases in his new chamber design.

[2] However, the new standardized ammunition and brass is not built to exactly the same dimensional specifications as the original wildcat or the dimensions listed on this page.

Moreover, Ackley's Pocket Manual for Shooters and Reloaders shows the rim thickness for his wildcat to range between .069" and .063" which is consistent with the Hornady handbook.

There is another size issue: according to Ackley's manual, his wildcat cartridge is only .289" over the shoulder while the Hornady factory round measures .294".

This fixes the bullet jump issue and improves ammunition availability with little risk of diminished performance.